The invention relates generally to an apparatus for the coating of members with a hardenable material in flowable state. More particularly, the invention relates to an apparatus for the coating of members with solder such as, for example, soft solder, with special emphasis on arrangements wherein the surge technique is used to apply the molten solder to the member. The case of particular interest is that where the member to be coated is provided with one or more passages.
The application of molten soft solder to members capable of being wetted thereby so as to coat the members with solder is already known. The so-called "surge technique" wherein the member to be coated is passed through a stream or wave of molten solder has also become known. The term "surge technique" as used herein encompasses substantially all processes wherein a motion is imparted to any type of molten solder. In addition, it is also known to use the surge technique for applying molten solder to metal-coated or metallized printed circuit boards. It is further known to provide such boards with bores or passages prior to application of the molten solder thereto, these bores or passages being required during subsequent use of the boards. This sequence of steps, i.e. providing the boards with passages prior to application of the molten solder thereto, is advantageous from the point of view that the stamping or boring tools used to make the passages would become rapidly contaminated by the soft solder, were the passages to be made subsequent to application of the solder to the boards.
However, the application of molten solder to metallized printed circuit boards provided with passages leads to the problem that the solder may readily flow across the openings of the passages and/or into the passages. Thus, when the solder solidifies, the passages may be partially or completely blocked by solder which has solidified across the openings thereof or by solder which has flowed into the passages.